The Niger army previously said Sunday that ten soldiers were killed in the assault near the border with Nigeria.
"In the night from Saturday to Sunday, the military post of Bla Brin was attacked by the terrorist group Boko Haram, we deplore the deaths of six soldiers and three wounded," said a defence ministry statement read out on state radio on Tuesday, without giving a reason for the revised death toll.
In late April, Niamey announced a military operation against Boko Haram in the region of Lake Chad, which links Niger, Chad, Nigeria and Cameroon.
The group, which is seeking an Islamic state based on Sharia law, has caused the deaths of at least 20,000 people since it took up arms in 2009 in Nigeria.
Some 2.4 million people have been displaced in northern Nigeria, Cameroon, Chad and Niger, according to the UN refugee agency UNHCR.--AFP